The present invention relates to a sensor system, and more particularly to a turbofan engine having a positional measurement system for a fan variable area nozzle structure within the fan nacelle thereof.
Conventional gas turbine engines include a fan section and a core engine with the fan section having a larger diameter than that of the core engine. The fan section and the core engine are disposed in series along a longitudinal axis and are enclosed in a nacelle. An annular stream of primary airflow passes through a radially inner portion of the fan section and through the core engine to generate primary thrust.
Combustion gases are discharged from the core engine through a primary airflow path and are exhausted through a core exhaust nozzle. An annular fan flow path, disposed radially outwardly of the primary airflow path, passes through a radial outer portion between a fan nacelle and a core nacelle and is discharged through an annular fan exhaust nozzle defined at least partially by the fan nacelle and the core nacelle to generate fan thrust. A majority of propulsion thrust is provided by the pressurized fan air discharged through the fan exhaust nozzle, the remaining thrust provided from the combustion gases discharged through the core exhaust nozzle.
The fan nozzles of conventional gas turbine engines have fixed geometry. The fixed geometry fan nozzles must be suitable for take-off and landing conditions as well as for cruise conditions. However, the requirements for take-off and landing conditions are different from requirements for the cruise condition. Optimum performance of the engine may be achieved during different flight conditions of an aircraft by tailoring the fan exhaust nozzle for the specific flight regimes.
Some gas turbine engines have implemented fan variable area nozzles. The fan variable area nozzle provides a smaller fan exit nozzle diameter during cruise conditions and a larger fan exit nozzle diameter during take-off and landing conditions. Conventional variable area nozzles typically utilize relatively complex mechanisms to determine the position of the variable area nozzle. Typically, a linkage interconnects the fan variable area nozzle to a linear variable displacement transducer to mechanically interpret the fan variable area nozzle position. Although effective, the linkage may be relatively complicated and heavy in weight—especially for a fan variable area nozzle capable of asymmetric operation which requires multiple sets of linkages.
Accordingly, it is desirable to provide an effective, lightweight position determination system for a gas turbine engine fan variable area nozzle.